Field of the Invention
The present invention relates to a catalysis combustion type gas sensor that detects an inflammable gas, and particularly, to a technique that makes the detection sensitivity of the inflammable gas higher in the catalysis combustion type gas sensor.
Priority is claimed on Japanese Patent Application No. 2014-187772, filed Sep. 16, 2014, the content of which is incorporated herein by reference.
Description of Related Art
In the related art, catalysis combustion type gas sensors, which combust an inflammable gas by using a catalyst and electrically detect a rise in the temperature of the catalyst caused by combustion heat, have been used as gas sensors that detect inflammable gases, such as hydrogen. Even in such catalysis combustion type gas sensors, similar to various sensors, it is always required to make the detection sensitivity higher, and high sensitivity is achieved by various methods. For example, Japanese Unexamined Patent Application No. 2001-99801 suggests that, in order to enhance gas detection sensitivity with respect to a low-concentration inflammable gas or an inflammable gas with low sensitivity, a heater for promoting combustion of the inflammable gas is formed in the vicinity of a catalyst layer (gas detection film) that acts as a catalyst with respect to the combustion of the inflammable gas.
However, when the gas detection film is heated by the heater, the heat generated by the heater is not uniformly transferred to the gas detection film, and temperature unevenness may occur in the gas detection film. Additionally, if the distribution of catalyst particles or film thickness in the gas detection film itself is uneven, there is a possibility that the amount of generated heat caused by the combustion of the inflammable gas becomes uneven, and the temperature unevenness occurs in the gas detection film. Generally, since the activity of a combustion catalyst that combusts an inflammable gas depends strongly on temperature, if the temperature unevenness occurs and a low-temperature region is formed, the amount of catalytic combustion decrease greatly in the region. Therefore, if the temperature unevenness occurs, there is a concern that the amount of catalytic combustion of the inflammable gas in the entire gas reaction film may decrease, and the detection sensitivity of the gas may degrade.